Information, and for that matter data, is a valuable asset. It will be appreciated by those skilled in the art that the probability of data being corrupted due to an error, malfunction, intentional damage and the like is considered an inevitable event and cannot be ignored.
Data backup systems are known in the art and are used to obtain and manage copies of the backed up information. To store the backed up information, these systems use different storage devices such as hard disk drives and tape drives. Conventional backup systems are divided into three categories, which are online backup systems, near line backup systems and off line backup systems (batch backup systems).
Information retaining systems often operate within the backed up system, and include at least one additional hard-disk-drive and continuously maintain a copy of the backed up information on that additional hard-disk-drive. One method for use in such systems is known as Mirroring, wherein the backed up hard-disk-drive is copied in full onto a backup hard-disk-drive.
Another information-retaining system is known as RAID and is provided in a number of levels. For example, RAID level 5 requires at least two additional hard-disk-drives, to the primary drive. If for any reason, one of the hard-disk-drives fails, the system automatically recovers the lost portions of data, from the remaining hard-disk-drives to a new hard drive, which replaces the hard-drive that failed. RAID systems, Mirror systems, Cluster systems and others are known in the art as fault tolerance systems. Such systems conventionally do not preserve multi-generation historical versions of the information.
Conventional backup systems perform two types of backup sessions—full backup session and modified backup session. In a full backup session, the backup system literally makes a complete copy of the entire amount of the information. During a modified backup session, the system detects any difference between the latest backup copy and the latest version of the backed up information, and stores only that difference. It is noted that a full backup session generally requires large amounts of time and media. However, full backup sessions should be performed regularly, in order to maintain the integrity of the data. Conventional data backup systems back up the information for which they are responsible, using one of the following methods which are: full backup method, differential backup method and incremental backup method. In a full backup methodology, all backup sessions are full backup sessions.
According to the differential and incremental backup methods, both full and modified backup sessions are held. For example, a full backup session may be performed once a week, while a modified backup session is held every hour.
According to the differential backup method, during a modified backup session the system backs up the data which has been modified since the most recent full backup session. According to the incremental backup method, during a modified backup session the system backs up the data which has been modified since the most recent full or modified backup session.
Network backup systems are also known in the art. Such a system is coupled with the backed up nodes via network communication and has clients running on each of the backed up nodes, which determine the portions and nature of the data which is to be backed up.